There are several ways how the energy can be extracted from a black hole [1]}, [2]}, [3]}. Penrose process states that in the ergoregion of a rotating black hole the particles with negative energy might exist due to collision or decay. As the result the energy of escaping particle is bigger than the energy of the original particle. This process is possible only in the ergorigion where the Killing vector \(\frac{d}{dt}\)  becomes spacelike. In spherical symmetry, i.e. for Schwarzschild and Reissner-Nordstrom black holes the Killing vector \(\frac{d}{dt}\)  is timelike outside the event horizon and the Penrose process is impossible. However, in Reissner-Nordstrom case, one can consider the analogy of the Penrose effect because there are charged particles with negative energy [4]}. These particles can exist only in the generalized ergoregion [5]}. The border of this region is called generalized ergosphere and it depends on the test particle parameters. Thus, even in the spherically-symmetric case there is the analogue of the Penrose process for charged black holes [5]}, [7]}.
